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Structural study of a mutant type I collagen from a patient with osteogenesis imperfecta
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Abstracts from the Calcified Tissues Workshop diameters in the “empty” and “amorphous” groupscompared to the “crystal” and “rupture.” Conclusion: The maturation of the vesicle is via diameter growth, directly related to the appearance of crystal. 6. Vesicles with ruptured membranes were closest to the front followed by “crystal, ” “amorphic” and “empty.”
STRUCTURAL STUDY OF A MUTANT TYPE I COLLAGEN FROM A PATIENT WITH OSTEOGENESIS IMPERFECTA W. Traub,* B. Steinmannt *Structural Chemistry Dept. Weizmann Institute, Rehovot, Israel, tpediatrics Department, University of Zurich, Zurich, Switzerland Osteogenesis imperfecta, or brittle bone syndrome, is a hereditary birth defect, which occurs in several forms, with symptoms of varying severity. In recent years, a number of mutant forms of the connective tissue protein collagen have been identified in patients with Osteogenesis Imperfecta. Several, but not all, of these mutations have proved lethal. We have studied a lethal mutant of type I collagen in which cysteine is substituted for glycine at position 988, near the C-terminal end of the triple-helical domain of the al (I) chains. Molecules containing either one or two such mutant chains were found to undergo excessive lysyl hydroxylation and hydroxylysyl glycosylation, and to have a melting temperature 3” below the normal 41°C. Increased intracellular degradation, delayed secretion, decreased extracellular collagen, and unusually small fibril diameters were also observed.’ We have built molecular models incorporating one mutant al(l) chain, or two with an interchain intramolecular disulphide bond. In either case, the mutant cysteine residues can only be accommodated with considerable distortion of the native collagen structure, with disruption of interchain contacts, including some degree of hydrogen bonding. However, the model studies do show that the disturbance in the triple helix is probably limited to a small local region. This suggests that the most important consequence of the mutation may be delayed molecular folding leading to decreased collagen production and fibril assembly, rather than the structural abnormality of the folded molecules, which are only marginally unstable. 1 8. Steinmann, V.H Rao. A Vogel, P. Bruckner, R. Gitzelmann and P.H. Byers. J Biol Chem 259, 11129-11138 (1984)
IMMUNE FUNCTION IN OSTEOPOROSIS: A CENTRAL ROLE FOR PERIPHERAL BLOOD MONOCYTES IN IMMUNE SUPPRESSION AND OSTEOPENIA J.S. Duke-Cohan, R. Sharon, N. Husseini, I. Leichter, D. Naor, H. Weinberg Dept. of Immunology, Hebrew University Medical School, Blood Bank, Dept. of Orthopaedics and Jerusalem Osteporosis Center, Hadassah; Jerusalem, Israel One certainty concerning the osteoporotic process is that there exists an imbalance of osteoblast and osteoclast activity, irrespective of absolute levels. Since the majority of known regulators of osteoclast function are associated with the immune system (T and B cell Osteoclast-Activating Factors, Interleukin 1, Monocytes, and the prostaglandins that they secrete) we have been investigating im-
mune function in osteoporosis. To this end we have found that cells from severe osteoporotics respond normally to the mitogens Concanavilin A(ConA), and Phytohaemagglutinin (PHA) and respond well in the Mixed Leukocyte Reaction (MLR), when responding in normal pooled human plasma, but when responding in autologous plasma the response in the MLR is severely reduced, while the mitogen responses are left relatively intact, indicating a relatively specific suppressor factor in OP plasma. We have found that indomethacin will considerably ameliorate the suppression by OP plasma, which also suppresses the response of normal cells, implying that prostaglandin synthesis, probably by monocytes is involved, but not PG’s themselves since lipid extraction of the plasma does not remove the suppression. In addition, we have found that there are increased levels of circulating monocytes in osteoporotics, monocytes being essential for the development of an MLR but suppressive in increased levels. The plasma suppression, removal by indomethacin, and increased monocytes were less apparent in mild or borderline osteoporosis, implying that immunosuppression was a concurrent or resultant process rather than a cause of osteopaenia. We suggest that monocytes mediate both the immune suppression and osteoclast activation.
PROLIFERATION, MATURATION, AGING AND TRANSFORMATION INTO BONE OF EMBRYONAL CHONDROCYTES IMPLANTED IN ARTICULAR DEFECTS S. Itay,*t Z. Nevo,T A. Abramovici,**
Z. Yosipovitch*
*Orthopaedics and **Pathology, Beilinson Medical Center, Petah Tiqva, tchemical Pathol., Tel Hashomer Tel Aviv University, Sackler Med. School, Israel Cultured embryonal chick epiphyseal chondrocytes were transplanted into full thickness defects in condylar articular cartilage of the tibio-torsal joints of roosters. The development in the implant of hyaline cartilage in the upper zones and bone below the osteochondral junction, was followed by histological, and histochemical techniques as well as by biochemical analyses for a period of 18 months. Active chondrocyte proliferation started within 48 hours from implantation. A gradual decrease in cell proliferation concomitantly with the formation of hyaline matrix surrounding the cells was noticed at two weeks post transplantation. Within eight weeks the defects were completely filled with hyaline cartilage. With time, further maturation occurs with differential appearance in the deep and superficial zones. While primary signs of cartilage-bone transformation start below the ossification front in two months, by six months this region is penetrated by vascular elements and young bone trabeculae, and by 18 months the tissue is completely transformed into bone. The articular zone of the implant preserved its cartilaginous phenotype along the 18 months followup period. In summary, the proliferation maturation aging and transformation into bone mimics basically the natural changes occurring during the normal life cycle.
MINERAL CONTENT OF THE RADIUS IN TRAINED AND UNTRAINED AGED PEOPLE E. Steinhagen-Thiessen, J.-D. Ringe, F. Ibbeken, G.V. Appen, H.-P. Meier-Baumgartner University Hospital, Medical Clinic, Hamburg, FRG
Abstracts from the Calcified Tissues Workshop diameters in the “empty” and “amorphous” groupscompared to the “crystal” and “rupture.” Conclusion: The maturation of the vesicle is via diameter growth, directly related to the appearance of crystal. 6. Vesicles with ruptured membranes were closest to the front followed by “crystal, ” “amorphic” and “empty.”
STRUCTURAL STUDY OF A MUTANT TYPE I COLLAGEN FROM A PATIENT WITH OSTEOGENESIS IMPERFECTA W. Traub,* B. Steinmannt *Structural Chemistry Dept. Weizmann Institute, Rehovot, Israel, tpediatrics Department, University of Zurich, Zurich, Switzerland Osteogenesis imperfecta, or brittle bone syndrome, is a hereditary birth defect, which occurs in several forms, with symptoms of varying severity. In recent years, a number of mutant forms of the connective tissue protein collagen have been identified in patients with Osteogenesis Imperfecta. Several, but not all, of these mutations have proved lethal. We have studied a lethal mutant of type I collagen in which cysteine is substituted for glycine at position 988, near the C-terminal end of the triple-helical domain of the al (I) chains. Molecules containing either one or two such mutant chains were found to undergo excessive lysyl hydroxylation and hydroxylysyl glycosylation, and to have a melting temperature 3” below the normal 41°C. Increased intracellular degradation, delayed secretion, decreased extracellular collagen, and unusually small fibril diameters were also observed.’ We have built molecular models incorporating one mutant al(l) chain, or two with an interchain intramolecular disulphide bond. In either case, the mutant cysteine residues can only be accommodated with considerable distortion of the native collagen structure, with disruption of interchain contacts, including some degree of hydrogen bonding. However, the model studies do show that the disturbance in the triple helix is probably limited to a small local region. This suggests that the most important consequence of the mutation may be delayed molecular folding leading to decreased collagen production and fibril assembly, rather than the structural abnormality of the folded molecules, which are only marginally unstable. 1 8. Steinmann, V.H Rao. A Vogel, P. Bruckner, R. Gitzelmann and P.H. Byers. J Biol Chem 259, 11129-11138 (1984)
IMMUNE FUNCTION IN OSTEOPOROSIS: A CENTRAL ROLE FOR PERIPHERAL BLOOD MONOCYTES IN IMMUNE SUPPRESSION AND OSTEOPENIA J.S. Duke-Cohan, R. Sharon, N. Husseini, I. Leichter, D. Naor, H. Weinberg Dept. of Immunology, Hebrew University Medical School, Blood Bank, Dept. of Orthopaedics and Jerusalem Osteporosis Center, Hadassah; Jerusalem, Israel One certainty concerning the osteoporotic process is that there exists an imbalance of osteoblast and osteoclast activity, irrespective of absolute levels. Since the majority of known regulators of osteoclast function are associated with the immune system (T and B cell Osteoclast-Activating Factors, Interleukin 1, Monocytes, and the prostaglandins that they secrete) we have been investigating im-
mune function in osteoporosis. To this end we have found that cells from severe osteoporotics respond normally to the mitogens Concanavilin A(ConA), and Phytohaemagglutinin (PHA) and respond well in the Mixed Leukocyte Reaction (MLR), when responding in normal pooled human plasma, but when responding in autologous plasma the response in the MLR is severely reduced, while the mitogen responses are left relatively intact, indicating a relatively specific suppressor factor in OP plasma. We have found that indomethacin will considerably ameliorate the suppression by OP plasma, which also suppresses the response of normal cells, implying that prostaglandin synthesis, probably by monocytes is involved, but not PG’s themselves since lipid extraction of the plasma does not remove the suppression. In addition, we have found that there are increased levels of circulating monocytes in osteoporotics, monocytes being essential for the development of an MLR but suppressive in increased levels. The plasma suppression, removal by indomethacin, and increased monocytes were less apparent in mild or borderline osteoporosis, implying that immunosuppression was a concurrent or resultant process rather than a cause of osteopaenia. We suggest that monocytes mediate both the immune suppression and osteoclast activation.
PROLIFERATION, MATURATION, AGING AND TRANSFORMATION INTO BONE OF EMBRYONAL CHONDROCYTES IMPLANTED IN ARTICULAR DEFECTS S. Itay,*t Z. Nevo,T A. Abramovici,**
Z. Yosipovitch*
*Orthopaedics and **Pathology, Beilinson Medical Center, Petah Tiqva, tchemical Pathol., Tel Hashomer Tel Aviv University, Sackler Med. School, Israel Cultured embryonal chick epiphyseal chondrocytes were transplanted into full thickness defects in condylar articular cartilage of the tibio-torsal joints of roosters. The development in the implant of hyaline cartilage in the upper zones and bone below the osteochondral junction, was followed by histological, and histochemical techniques as well as by biochemical analyses for a period of 18 months. Active chondrocyte proliferation started within 48 hours from implantation. A gradual decrease in cell proliferation concomitantly with the formation of hyaline matrix surrounding the cells was noticed at two weeks post transplantation. Within eight weeks the defects were completely filled with hyaline cartilage. With time, further maturation occurs with differential appearance in the deep and superficial zones. While primary signs of cartilage-bone transformation start below the ossification front in two months, by six months this region is penetrated by vascular elements and young bone trabeculae, and by 18 months the tissue is completely transformed into bone. The articular zone of the implant preserved its cartilaginous phenotype along the 18 months followup period. In summary, the proliferation maturation aging and transformation into bone mimics basically the natural changes occurring during the normal life cycle.
MINERAL CONTENT OF THE RADIUS IN TRAINED AND UNTRAINED AGED PEOPLE E. Steinhagen-Thiessen, J.-D. Ringe, F. Ibbeken, G.V. Appen, H.-P. Meier-Baumgartner University Hospital, Medical Clinic, Hamburg, FRG